The present invention relates generally to engine exhaust systems and more particularly to an exhaust system for an engine that is utilized for powering a straddle carrier that consists of a large inverted U-shaped frame that defines a cargo carrying space between the legs of the U-shaped frame.
Various types of straddle carriers for transporting large containers which are on the order of twenty to forty feet long have been proposed. One such type of container that has recently been developed is disclosed in U.S. patent application Ser. No. 844,655, filed Oct. 25, 1977, which has been accepted in the industry as a significant major contribution in the area of cargo container carrying vehicles. One of the significant improvements that is incorporated into this type of vehicle is that the entire system is hydraulic and the various hydraulic drive components and control functions are powered by two separate engines. It will be appreciated that in this type of vehicle, the interconnecting web between the vertical legs of the U-shaped frame is located more than 20 feet above the ground level and the cab structure for the operator must of necessity be located above the horizontal web of frame 14 so that the operator has clear visibility of the container located in the cargo container bay during attachment and detachment of a spreader with the container.
One of the significant improvements from a commercial acceptance point of view of the straddle carrier disclosed in the above-identified application, is the fact that the respective engines are located at the lower end of the respective legs of the inverted U-shaped frame so the various major components are located in close proximity to the ground and the majority of the weight is close to the ground engaging wheels. For example, the unit disclosed in the above-identified application has a pair of pumps driven by each of the engines and one of the pumps of each pair supplies pressurized hydraulic fluid to a hydrostatic drive system that is associated with the wheels on an associated leg of the inverted U-shaped frame. A second pump of each pair supplies the hydraulic pressurized fluid to a hoisting cylinder that is associated with each leg of the inverted U-shaped carrier frame and other control functions. Thus, having all of these components in close proximity to the ground reduces the amount of extremely heavy duty flexible hosing that is necessary for connecting the respective pumps to the reservoir and to the various components that are supplied with pressurized hydraulic fluid.
One of the significant problems that had to be overcome with the innovative vehicle that was developed was the control of the exhaust gases from the respective engines which of necessity had to be exhausted at a level above the level of the cab structure in which the operator is located. To alleviate this problem, the unique straddle carrier disclosed in the above application incorporates an exhaust system wherein the exhaust gases are exhausted at a level above the cab for the vehicle without creating any undue back pressure into the engines for the vehicle. This is accomplished by having a very short exhaust line which has an outlet end in close proximity to the vehicle engine and an enlarged pipe having one end surrounding the outlet end of the exhaust line and being larger to produce an annular opening adjacent the exhaust outlet while the opposite end is located above the cab structure for the straddle carrier. The enlarged annular opening created a chimney effect for drawing air into the lower end of the enlarged pipe which produces a positive flow throughout the length of the enlarged pipe. In fact, it was determined that this type of exhaust system resulted in a lower back pressure to the engine than most conventional exhaust systems that are presently utilized with large engines of this type, which normally are diesel engines.
However, during use of this type of straddle carrier, one of the objections that was received from the operators was the fact that the crankcase ventilation, which included a drainpipe from the vent outlet of the crankcase towards the ground, resulted in nauseous fumes being located in an area surrounding the engine. In addition, the operators complained that many times combustible liquids were being deposited on the ground adjacent the vehicle as well as certain parts of the frame structure of the vehicle which not only is distasteful from an appearance standpoint, but more importantly could easily result in a fire hazard.